Method for product recovery of polyolefins

Abstract

A method for product recovery method of polyolefins, particularly high-molecular-weight amorphous poly alpha-olefins, wherein the use of water during the method is significantly decreased and wherein the intermediate stage of storing and drying the chunk form of the polyolefin is eliminated. Polyolefins produced in a reactor are heated in a kneader to remove any unreacted monomer(s). The polyolefin material in a liquid form is then transferred directly to an extruder to further remove any unreacted monomer(s) and catalyst(s). Finally, the polyolefin material is pelletized using a pelletizer.

I claim: 
     
       1. A method for the recovery of a high-molecular-weight amorphous polyolefin comprising: reacting monomer(s) in a reaction zone to form a high-molecular-weight amorphous polyolefin;   continuously transferring blips of material containing the polyolefin along with residual catalyst and unreacted monomer(s) as a mixture from the reaction zone to a recovery zone;   venting unreacted monomer(s) from the recovery zone;   controlling the transfer of the material blips into the recovery zone without introducing water and while substantially avoiding carryover of the polyolefin back to the reaction zone during the venting step;   heating the mixture of said material blips in the recovery zone to a temperature of at least about 250° F. while kneading the mixture for a time sufficient to remove unreacted monomer(s) from the polyolefin and to facilitate transfer of recovered polyolefin from the recovery zone to an extrusion zone; and   controlling the material blip transfer, heating, and kneading steps to maintain a substantially constant inventory of the polyolefin in the recovery zone.   
     
     
       2. The method of claim 1, which further comprises recycling the vented unreacted monomer(s) back to the reaction zone. 
     
     
       3. The method of claim 1, which further comprises deactivating residual catalyst contained in the polyolefin in the extrusion zone. 
     
     
       4. The method of claim 3, which further comprises: deactivating the catalyst by mixing the polyolefin with steam in the extrusion zone; and   removing steam and additional unreacted monomer(s) from the polyolefin in extrusion zone by venting.   
     
     
       5. The method of claim 1, wherein the kneading step comprises mechanically working the polyolefin in the recovery zone by passing the polyolefin through rotating sigma blades to facilitate the removal of unreacted monomer(s). 
     
     
       6. The method of claim 4, which further comprises controlling the temperature of the polyolefin in the extrusion zone to be substantially the same as the temperature of the polyolefin in the recovery zone. 
     
     
       7. The method of claim 4, which further comprises heating the polyolefin in the extrusion zone to facilitate the venting of steam and the removal of remaining unreacted monomer(s). 
     
     
       8. A method for the recovery of a high-molecular-weight amorphous polyolefin which comprises: reacting monomer(s) in a reactor to form a high molecular weight amorphous polyolefin;   continuously transferring blips of material containing the polyolefin along with residual catalyst and unreacted monomer(s) as a mixture from the reactor directly through a conduit which contains a blipper valve to a kneader, the kneader having rotatable sigma blades, a kneader vent line and a kneader vent valve for venting unreacted monomer(s);   venting unreacted monomer(s) from the kneader through the vent line and vent valve;   controlling the operation of the blipper valve and the kneader vent valve to transfer material blips from the reactor to the kneader primarily when the blipper valve is open and when the kneader vent valve is closed to substantially avoid carryover of polyolefin into the kneader vent line during the venting step;   heating the mixture of material blips in the kneader to a temperature of from about 250° F. to 500° F. while kneading the mixture for a time sufficient to remove unreacted monomer(s) from the polyolefin and to facilitate transfer of the recovered polyolefin from the kneader to an extruder; and   controlling the material blip transfer, heating and kneading steps to maintain a substantially constant inventory of the polyolefin in the kneader.   
     
     
       9. The method of claim 8, which further comprises deactivating residual catalyst contained in the polyolefin in the extruder. 
     
     
       10. The method of claim 9, which further comprises deactivating the catalyst by mixing the polyolefin with steam in the extruder. 
     
     
       11. The method of claim 8, wherein the kneading step comprises mechanically working the polyolefin in the kneader by rotating the sigma blades for a time sufficient to facilitate the removal of unreacted monomer(s). 
     
     
       12. The method of claim 8, which further comprises controlling the temperature of the polyolefin in the extruder to be substantially the same as the temperature of the polyolefin in the kneader. 
     
     
       13. The method of claim 9, which further comprises heating the polyolefin in the extruder to facilitate the venting of steam and the removal of remaining unreacted monomer(s). 
     
     
       14. The method of claim 8, wherein the material blips are transferred to the recovery zone without introducing water therein. 
     
     
       15. A method for the recovery of a high-molecular-weight sticky amorphous polyolefin which consists essentially of: reacting monomer(s) in a reactor to form a high molecular weight amorphous polyolefin;   continuously transferring blips of material containing the polyolefin along with residual catalyst and unreacted monomer(s) as a mixture from the reactor directly through a conduit which contains a blipper valve to a kneader, the kneader having rotatable sigma blades, a kneader vent line and a kneader vent valve for venting unreacted monomer(s);   venting unreacted monomer(s) from the kneader through the vent line and vent valve;   controlling the operation of the blipper valve and the kneader vent valve to transfer material blips from the reactor to the kneader without introducing water and primarily when the blipper valve is open and when the kneader vent valve is closed to substantially avoid carryover of polyolefin into the kneader vent line during the venting step;   heating the mixture of material blips in the kneader to a temperature of from about 250° F. to 500° F. while kneading the mixture for a time sufficient to remove unreacted monomer(s) from the polyolefin and to facilitate transfer of the recovered polyolefin from the kneader to an extruder;   controlling the material blip transfer, heating and kneading steps to maintain a substantially constant inventory of the polyolefin in the kneader;   recovering the polyolefin from the kneader;   transferring the recovered polyolefin from the kneader to an extruder; and   deactivating residual catalyst contained in the polyolefin by mixing the polyolefin in the extruder with steam in an amount sufficient only to deactivate the catalyst, but insufficient to transport the polyolefin.   
     
     
       16. The method of claim 1 which further comprises recovering the polyolefin from the recovery zone. 
     
     
       17. The method of claim 8 which further comprises recovering the polyolefin from the kneader. 
     
     
       18. The method of claim 17 which further comprises transferring the recovered polyolefin from the kneader to an extruder.